kernel/kmod.c

   1 /*
   2         kmod, the new module loader (replaces kerneld)
   3         Kirk Petersen
   4
   5         Reorganized not to be a daemon by Adam Richter, with guidance
   6         from Greg Zornetzer.
   7
   8         Modified to avoid chroot and file sharing problems.
   9         Mikael Pettersson
  10
  11         Limit the concurrent number of kmod modprobes to catch loops from
  12         "modprobe needs a service that is in a module".
  13         Keith Owens <kaos@ocs.com.au> December 1999
  14
  15         Unblock all signals when we exec a usermode process.
  16         Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
  17
  18         call_usermodehelper wait flag, and remove exec_usermodehelper.
  19         Rusty Russell <rusty@rustcorp.com.au>  Jan 2003
  20 */
  21 #include <linux/module.h>
  22 #include <linux/sched.h>
  23 #include <linux/syscalls.h>
  24 #include <linux/unistd.h>
  25 #include <linux/kmod.h>
  26 #include <linux/slab.h>
  27 #include <linux/completion.h>
  28 #include <linux/cred.h>
  29 #include <linux/file.h>
  30 #include <linux/fdtable.h>
  31 #include <linux/workqueue.h>
  32 #include <linux/security.h>
  33 #include <linux/mount.h>
  34 #include <linux/kernel.h>
  35 #include <linux/init.h>
  36 #include <linux/resource.h>
  37 #include <linux/notifier.h>
  38 #include <linux/suspend.h>
  39 #include <linux/rwsem.h>
  40 #include <linux/ptrace.h>
  41 #include <asm/uaccess.h>
  42
  43 #include <trace/events/module.h>
  44
  45 extern int max_threads;
  46
  47 static struct workqueue_struct *khelper_wq;
  48
  49 /*
  50  * kmod_thread_locker is used for deadlock avoidance.  There is no explicit
  51  * locking to protect this global - it is private to the singleton khelper
  52  * thread and should only ever be modified by that thread.
  53  */
  54 static const struct task_struct *kmod_thread_locker;
  55
  56 #define CAP_BSET        (void *)1
  57 #define CAP_PI          (void *)2
  58
  59 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
  60 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
  61 static DEFINE_SPINLOCK(umh_sysctl_lock);
  62 static DECLARE_RWSEM(umhelper_sem);
  63
  64 #ifdef CONFIG_MODULES
  65
  66 /*
  67         modprobe_path is set via /proc/sys.
  68 */
  69 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
  70
  71 static void free_modprobe_argv(struct subprocess_info *info)
  72 {
  73         kfree(info->argv[3]); /* check call_modprobe() */
  74         kfree(info->argv);
  75 }
  76
  77 static int call_modprobe(char *module_name, int wait)
  78 {
  79         static char *envp[] = {
  80                 "HOME=/",
  81                 "TERM=linux",
  82                 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
  83                 NULL
  84         };
  85
  86         char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
  87         if (!argv)
  88                 goto out;
  89
  90         module_name = kstrdup(module_name, GFP_KERNEL);
  91         if (!module_name)
  92                 goto free_argv;
  93
  94         argv[0] = modprobe_path;
  95         argv[1] = "-q";
  96         argv[2] = "--";
  97         argv[3] = module_name;  /* check free_modprobe_argv() */
  98         argv[4] = NULL;
  99
 100         return call_usermodehelper_fns(modprobe_path, argv, envp,
 101                 wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
 102 free_argv:
 103         kfree(argv);
 104 out:
 105         return -ENOMEM;
 106 }
 107
 108 /**
 109  * __request_module - try to load a kernel module
 110  * @wait: wait (or not) for the operation to complete
 111  * @fmt: printf style format string for the name of the module
 112  * @...: arguments as specified in the format string
 113  *
 114  * Load a module using the user mode module loader. The function returns
 115  * zero on success or a negative errno code on failure. Note that a
 116  * successful module load does not mean the module did not then unload
 117  * and exit on an error of its own. Callers must check that the service
 118  * they requested is now available not blindly invoke it.
 119  *
 120  * If module auto-loading support is disabled then this function
 121  * becomes a no-operation.
 122  */
 123 int __request_module(bool wait, const char *fmt, ...)
 124 {
 125         va_list args;
 126         char module_name[MODULE_NAME_LEN];
 127         unsigned int max_modprobes;
 128         int ret;
 129         static atomic_t kmod_concurrent = ATOMIC_INIT(0);
 130 #define MAX_KMOD_CONCURRENT 50  /* Completely arbitrary value - KAO */
 131         static int kmod_loop_msg;
 132
 133         va_start(args, fmt);
 134         ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 135         va_end(args);
 136         if (ret >= MODULE_NAME_LEN)
 137                 return -ENAMETOOLONG;
 138
 139         ret = security_kernel_module_request(module_name);
 140         if (ret)
 141                 return ret;
 142
 143         /* If modprobe needs a service that is in a module, we get a recursive
 144          * loop.  Limit the number of running kmod threads to max_threads/2 or
 145          * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
 146          * would be to run the parents of this process, counting how many times
 147          * kmod was invoked.  That would mean accessing the internals of the
 148          * process tables to get the command line, proc_pid_cmdline is static
 149          * and it is not worth changing the proc code just to handle this case.
 150          * KAO.
 151          *
 152          * "trace the ppid" is simple, but will fail if someone's
 153          * parent exits.  I think this is as good as it gets. --RR
 154          */
 155         max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
 156         atomic_inc(&kmod_concurrent);
 157         if (atomic_read(&kmod_concurrent) > max_modprobes) {
 158                 /* We may be blaming an innocent here, but unlikely */
 159                 if (kmod_loop_msg < 5) {
 160                         printk(KERN_ERR
 161                                "request_module: runaway loop modprobe %s\n",
 162                                module_name);
 163                         kmod_loop_msg++;
 164                 }
 165                 atomic_dec(&kmod_concurrent);
 166                 return -ENOMEM;
 167         }
 168
 169         trace_module_request(module_name, wait, _RET_IP_);
 170
 171         ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
 172
 173         atomic_dec(&kmod_concurrent);
 174         return ret;
 175 }
 176 EXPORT_SYMBOL(__request_module);
 177 #endif /* CONFIG_MODULES */
 178
 179 /*
 180  * This is the task which runs the usermode application
 181  */
 182 static int ____call_usermodehelper(void *data)
 183 {
 184         struct subprocess_info *sub_info = data;
 185         struct cred *new;
 186         int retval;
 187
 188         spin_lock_irq(&current->sighand->siglock);
 189         flush_signal_handlers(current, 1);
 190         spin_unlock_irq(&current->sighand->siglock);
 191
 192         /* We can run anywhere, unlike our parent keventd(). */
 193         set_cpus_allowed_ptr(current, cpu_all_mask);
 194
 195         /*
 196          * Our parent is keventd, which runs with elevated scheduling priority.
 197          * Avoid propagating that into the userspace child.
 198          */
 199         set_user_nice(current, 0);
 200
 201         retval = -ENOMEM;
 202         new = prepare_kernel_cred(current);
 203         if (!new)
 204                 goto fail;
 205
 206         spin_lock(&umh_sysctl_lock);
 207         new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
 208         new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
 209                                              new->cap_inheritable);
 210         spin_unlock(&umh_sysctl_lock);
 211
 212         if (sub_info->init) {
 213                 retval = sub_info->init(sub_info, new);
 214                 if (retval) {
 215                         abort_creds(new);
 216                         goto fail;
 217                 }
 218         }
 219
 220         commit_creds(new);
 221
 222         retval = kernel_execve(sub_info->path,
 223                                (const char *const *)sub_info->argv,
 224                                (const char *const *)sub_info->envp);
 225         if (!retval)
 226                 return 0;
 227
 228         /* Exec failed? */
 229 fail:
 230         sub_info->retval = retval;
 231         do_exit(0);
 232 }
 233
 234 static int call_helper(void *data)
 235 {
 236         /* Worker thread started blocking khelper thread. */
 237         kmod_thread_locker = current;
 238         return ____call_usermodehelper(data);
 239 }
 240
 241 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
 242 {
 243         if (info->cleanup)
 244                 (*info->cleanup)(info);
 245         kfree(info);
 246 }
 247
 248 static void umh_complete(struct subprocess_info *sub_info)
 249 {
 250         struct completion *comp = xchg(&sub_info->complete, NULL);
 251         /*
 252          * See call_usermodehelper_exec(). If xchg() returns NULL
 253          * we own sub_info, the UMH_KILLABLE caller has gone away.
 254          */
 255         if (comp)
 256                 complete(comp);
 257         else
 258                 call_usermodehelper_freeinfo(sub_info);
 259 }
 260
 261 /* Keventd can't block, but this (a child) can. */
 262 static int wait_for_helper(void *data)
 263 {
 264         struct subprocess_info *sub_info = data;
 265         pid_t pid;
 266
 267         /* If SIGCLD is ignored sys_wait4 won't populate the status. */
 268         spin_lock_irq(&current->sighand->siglock);
 269         current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
 270         spin_unlock_irq(&current->sighand->siglock);
 271
 272         pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
 273         if (pid < 0) {
 274                 sub_info->retval = pid;
 275         } else {
 276                 int ret = -ECHILD;
 277                 /*
 278                  * Normally it is bogus to call wait4() from in-kernel because
 279                  * wait4() wants to write the exit code to a userspace address.
 280                  * But wait_for_helper() always runs as keventd, and put_user()
 281                  * to a kernel address works OK for kernel threads, due to their
 282                  * having an mm_segment_t which spans the entire address space.
 283                  *
 284                  * Thus the __user pointer cast is valid here.
 285                  */
 286                 sys_wait4(pid, (int __user *)&ret, 0, NULL);
 287
 288                 /*
 289                  * If ret is 0, either ____call_usermodehelper failed and the
 290                  * real error code is already in sub_info->retval or
 291                  * sub_info->retval is 0 anyway, so don't mess with it then.
 292                  */
 293                 if (ret)
 294                         sub_info->retval = ret;
 295         }
 296
 297         umh_complete(sub_info);
 298         do_exit(0);
 299 }
 300
 301 /* This is run by khelper thread  */
 302 static void __call_usermodehelper(struct work_struct *work)
 303 {
 304         struct subprocess_info *sub_info =
 305                 container_of(work, struct subprocess_info, work);
 306         int wait = sub_info->wait & ~UMH_KILLABLE;
 307         pid_t pid;
 308
 309         /* CLONE_VFORK: wait until the usermode helper has execve'd
 310          * successfully We need the data structures to stay around
 311          * until that is done.  */
 312         if (wait == UMH_WAIT_PROC)
 313                 pid = kernel_thread(wait_for_helper, sub_info,
 314                                     CLONE_FS | CLONE_FILES | SIGCHLD);
 315         else {
 316                 pid = kernel_thread(call_helper, sub_info,
 317                                     CLONE_VFORK | SIGCHLD);
 318                 /* Worker thread stopped blocking khelper thread. */
 319                 kmod_thread_locker = NULL;
 320         }
 321
 322         switch (wait) {
 323         case UMH_NO_WAIT:
 324                 call_usermodehelper_freeinfo(sub_info);
 325                 break;
 326
 327         case UMH_WAIT_PROC:
 328                 if (pid > 0)
 329                         break;
 330                 /* FALLTHROUGH */
 331         case UMH_WAIT_EXEC:
 332                 if (pid < 0)
 333                         sub_info->retval = pid;
 334                 umh_complete(sub_info);
 335         }
 336 }
 337
 338 /*
 339  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
 340  * (used for preventing user land processes from being created after the user
 341  * land has been frozen during a system-wide hibernation or suspend operation).
 342  * Should always be manipulated under umhelper_sem acquired for write.
 343  */
 344 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 345
 346 /* Number of helpers running */
 347 static atomic_t running_helpers = ATOMIC_INIT(0);
 348
 349 /*
 350  * Wait queue head used by usermodehelper_disable() to wait for all running
 351  * helpers to finish.
 352  */
 353 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
 354
 355 /*
 356  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
 357  * to become 'false'.
 358  */
 359 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 360
 361 /*
 362  * Time to wait for running_helpers to become zero before the setting of
 363  * usermodehelper_disabled in usermodehelper_disable() fails
 364  */
 365 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
 366
 367 int usermodehelper_read_trylock(void)
 368 {
 369         DEFINE_WAIT(wait);
 370         int ret = 0;
 371
 372         down_read(&umhelper_sem);
 373         for (;;) {
 374                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 375                                 TASK_INTERRUPTIBLE);
 376                 if (!usermodehelper_disabled)
 377                         break;
 378
 379                 if (usermodehelper_disabled == UMH_DISABLED)
 380                         ret = -EAGAIN;
 381
 382                 up_read(&umhelper_sem);
 383
 384                 if (ret)
 385                         break;
 386
 387                 schedule();
 388                 try_to_freeze();
 389
 390                 down_read(&umhelper_sem);
 391         }
 392         finish_wait(&usermodehelper_disabled_waitq, &wait);
 393         return ret;
 394 }
 395 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
 396
 397 long usermodehelper_read_lock_wait(long timeout)
 398 {
 399         DEFINE_WAIT(wait);
 400
 401         if (timeout < 0)
 402                 return -EINVAL;
 403
 404         down_read(&umhelper_sem);
 405         for (;;) {
 406                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 407                                 TASK_UNINTERRUPTIBLE);
 408                 if (!usermodehelper_disabled)
 409                         break;
 410
 411                 up_read(&umhelper_sem);
 412
 413                 timeout = schedule_timeout(timeout);
 414                 if (!timeout)
 415                         break;
 416
 417                 down_read(&umhelper_sem);
 418         }
 419         finish_wait(&usermodehelper_disabled_waitq, &wait);
 420         return timeout;
 421 }
 422 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
 423
 424 void usermodehelper_read_unlock(void)
 425 {
 426         up_read(&umhelper_sem);
 427 }
 428 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 429
 430 /**
 431  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
 432  * @depth: New value to assign to usermodehelper_disabled.
 433  *
 434  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
 435  * writing) and wakeup tasks waiting for it to change.
 436  */
 437 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 438 {
 439         down_write(&umhelper_sem);
 440         usermodehelper_disabled = depth;
 441         wake_up(&usermodehelper_disabled_waitq);
 442         up_write(&umhelper_sem);
 443 }
 444
 445 /**
 446  * __usermodehelper_disable - Prevent new helpers from being started.
 447  * @depth: New value to assign to usermodehelper_disabled.
 448  *
 449  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
 450  */
 451 int __usermodehelper_disable(enum umh_disable_depth depth)
 452 {
 453         long retval;
 454
 455         if (!depth)
 456                 return -EINVAL;
 457
 458         down_write(&umhelper_sem);
 459         usermodehelper_disabled = depth;
 460         up_write(&umhelper_sem);
 461
 462         /*
 463          * From now on call_usermodehelper_exec() won't start any new
 464          * helpers, so it is sufficient if running_helpers turns out to
 465          * be zero at one point (it may be increased later, but that
 466          * doesn't matter).
 467          */
 468         retval = wait_event_timeout(running_helpers_waitq,
 469                                         atomic_read(&running_helpers) == 0,
 470                                         RUNNING_HELPERS_TIMEOUT);
 471         if (retval)
 472                 return 0;
 473
 474         __usermodehelper_set_disable_depth(UMH_ENABLED);
 475         return -EAGAIN;
 476 }
 477
 478 static void helper_lock(void)
 479 {
 480         atomic_inc(&running_helpers);
 481         smp_mb__after_atomic_inc();
 482 }
 483
 484 static void helper_unlock(void)
 485 {
 486         if (atomic_dec_and_test(&running_helpers))
 487                 wake_up(&running_helpers_waitq);
 488 }
 489
 490 /**
 491  * call_usermodehelper_setup - prepare to call a usermode helper
 492  * @path: path to usermode executable
 493  * @argv: arg vector for process
 494  * @envp: environment for process
 495  * @gfp_mask: gfp mask for memory allocation
 496  *
 497  * Returns either %NULL on allocation failure, or a subprocess_info
 498  * structure.  This should be passed to call_usermodehelper_exec to
 499  * exec the process and free the structure.
 500  */
 501 static
 502 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
 503                                                   char **envp, gfp_t gfp_mask)
 504 {
 505         struct subprocess_info *sub_info;
 506         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
 507         if (!sub_info)
 508                 goto out;
 509
 510         INIT_WORK(&sub_info->work, __call_usermodehelper);
 511         sub_info->path = path;
 512         sub_info->argv = argv;
 513         sub_info->envp = envp;
 514   out:
 515         return sub_info;
 516 }
 517
 518 /**
 519  * call_usermodehelper_setfns - set a cleanup/init function
 520  * @info: a subprocess_info returned by call_usermodehelper_setup
 521  * @cleanup: a cleanup function
 522  * @init: an init function
 523  * @data: arbitrary context sensitive data
 524  *
 525  * The init function is used to customize the helper process prior to
 526  * exec.  A non-zero return code causes the process to error out, exit,
 527  * and return the failure to the calling process
 528  *
 529  * The cleanup function is just before ethe subprocess_info is about to
 530  * be freed.  This can be used for freeing the argv and envp.  The
 531  * Function must be runnable in either a process context or the
 532  * context in which call_usermodehelper_exec is called.
 533  */
 534 static
 535 void call_usermodehelper_setfns(struct subprocess_info *info,
 536                     int (*init)(struct subprocess_info *info, struct cred *new),
 537                     void (*cleanup)(struct subprocess_info *info),
 538                     void *data)
 539 {
 540         info->cleanup = cleanup;
 541         info->init = init;
 542         info->data = data;
 543 }
 544
 545 /**
 546  * call_usermodehelper_exec - start a usermode application
 547  * @sub_info: information about the subprocessa
 548  * @wait: wait for the application to finish and return status.
 549  *        when -1 don't wait at all, but you get no useful error back when
 550  *        the program couldn't be exec'ed. This makes it safe to call
 551  *        from interrupt context.
 552  *
 553  * Runs a user-space application.  The application is started
 554  * asynchronously if wait is not set, and runs as a child of keventd.
 555  * (ie. it runs with full root capabilities).
 556  */
 557 static
 558 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 559 {
 560         DECLARE_COMPLETION_ONSTACK(done);
 561         int retval = 0;
 562
 563         helper_lock();
 564         if (sub_info->path[0] == '\0')
 565                 goto out;
 566
 567         if (!khelper_wq || usermodehelper_disabled) {
 568                 retval = -EBUSY;
 569                 goto out;
 570         }
 571         /*
 572          * Worker thread must not wait for khelper thread at below
 573          * wait_for_completion() if the thread was created with CLONE_VFORK
 574          * flag, for khelper thread is already waiting for the thread at
 575          * wait_for_completion() in do_fork().
 576          */
 577         if (wait != UMH_NO_WAIT && current == kmod_thread_locker) {
 578                 retval = -EBUSY;
 579                 goto out;
 580         }
 581
 582         sub_info->complete = &done;
 583         sub_info->wait = wait;
 584
 585         queue_work(khelper_wq, &sub_info->work);
 586         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 587                 goto unlock;
 588
 589         if (wait & UMH_KILLABLE) {
 590                 retval = wait_for_completion_killable(&done);
 591                 if (!retval)
 592                         goto wait_done;
 593
 594                 /* umh_complete() will see NULL and free sub_info */
 595                 if (xchg(&sub_info->complete, NULL))
 596                         goto unlock;
 597                 /* fallthrough, umh_complete() was already called */
 598         }
 599
 600         wait_for_completion(&done);
 601 wait_done:
 602         retval = sub_info->retval;
 603 out:
 604         call_usermodehelper_freeinfo(sub_info);
 605 unlock:
 606         helper_unlock();
 607         return retval;
 608 }
 609
 610 /*
 611  * call_usermodehelper_fns() will not run the caller-provided cleanup function
 612  * if a memory allocation failure is experienced.  So the caller might need to
 613  * check the call_usermodehelper_fns() return value: if it is -ENOMEM, perform
 614  * the necessaary cleanup within the caller.
 615  */
 616 int call_usermodehelper_fns(
 617         char *path, char **argv, char **envp, int wait,
 618         int (*init)(struct subprocess_info *info, struct cred *new),
 619         void (*cleanup)(struct subprocess_info *), void *data)
 620 {
 621         struct subprocess_info *info;
 622         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 623
 624         info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
 625
 626         if (info == NULL)
 627                 return -ENOMEM;
 628
 629         call_usermodehelper_setfns(info, init, cleanup, data);
 630
 631         return call_usermodehelper_exec(info, wait);
 632 }
 633 EXPORT_SYMBOL(call_usermodehelper_fns);
 634
 635 static int proc_cap_handler(struct ctl_table *table, int write,
 636                          void __user *buffer, size_t *lenp, loff_t *ppos)
 637 {
 638         struct ctl_table t;
 639         unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
 640         kernel_cap_t new_cap;
 641         int err, i;
 642
 643         if (write && (!capable(CAP_SETPCAP) ||
 644                       !capable(CAP_SYS_MODULE)))
 645                 return -EPERM;
 646
 647         /*
 648          * convert from the global kernel_cap_t to the ulong array to print to
 649          * userspace if this is a read.
 650          */
 651         spin_lock(&umh_sysctl_lock);
 652         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
 653                 if (table->data == CAP_BSET)
 654                         cap_array[i] = usermodehelper_bset.cap[i];
 655                 else if (table->data == CAP_PI)
 656                         cap_array[i] = usermodehelper_inheritable.cap[i];
 657                 else
 658                         BUG();
 659         }
 660         spin_unlock(&umh_sysctl_lock);
 661
 662         t = *table;
 663         t.data = &cap_array;
 664
 665         /*
 666          * actually read or write and array of ulongs from userspace.  Remember
 667          * these are least significant 32 bits first
 668          */
 669         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
 670         if (err < 0)
 671                 return err;
 672
 673         /*
 674          * convert from the sysctl array of ulongs to the kernel_cap_t
 675          * internal representation
 676          */
 677         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
 678                 new_cap.cap[i] = cap_array[i];
 679
 680         /*
 681          * Drop everything not in the new_cap (but don't add things)
 682          */
 683         spin_lock(&umh_sysctl_lock);
 684         if (write) {
 685                 if (table->data == CAP_BSET)
 686                         usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 687                 if (table->data == CAP_PI)
 688                         usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
 689         }
 690         spin_unlock(&umh_sysctl_lock);
 691
 692         return 0;
 693 }
 694
 695 struct ctl_table usermodehelper_table[] = {
 696         {
 697                 .procname       = "bset",
 698                 .data           = CAP_BSET,
 699                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 700                 .mode           = 0600,
 701                 .proc_handler   = proc_cap_handler,
 702         },
 703         {
 704                 .procname       = "inheritable",
 705                 .data           = CAP_PI,
 706                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 707                 .mode           = 0600,
 708                 .proc_handler   = proc_cap_handler,
 709         },
 710         { }
 711 };
 712
 713 void __init usermodehelper_init(void)
 714 {
 715         khelper_wq = create_singlethread_workqueue("khelper");
 716         BUG_ON(!khelper_wq);
 717 }